How I Built a Fintech Platform in My Late Thirties

I’ve studied at two of the most rigorous academic institutions, ITAM (Applied Mathematics) and Columbia (Public Administration). But when it came to the work that’s shaped me most, trading, financial modeling, corporate finance, credit underwriting, and building fintech platforms, I was never formally trained. No certification programs, no onboarding seminars, no workshops. I learned the hard way, by doing the work myself.

And that’s exactly how I ended up building a BNPL platform with a high-performing underwriting system, without a tech background or a tech cofounder.

The Problem I Saw

I had already learned credit underwriting while managing $500K–$1M corporate loans at Upton Financial. But the market I was stepping into was different. This was retail BNPL credit, loans of $100 to $1,000 to help people buy all kinds of things like TVs, refrigerators, or washing machines.

The opportunity was clear: there was huge demand and terrible execution across the board. Most lenders had default rates over 30%. I knew I could do better. So I got to work.

When Outsourcing Fails

I didn’t know how to code and I wasn’t a product manager. So I hired third-party developers, three different times. Each one failed. And after nearly 10 months, I had spent a significant amount of my own capital, and I had nothing to show for it but bad demos and broken promises. That was the first real test: Do I walk away, or do I build it myself? I chose the second.

Learning by Building

I hired a great programmer, and together, we built everything. I personally designed every inch of the platform, the full user experience, every form field, the complete onboarding flow, and most importantly: a risk management engine that analyzed 200+ data points per client. We even introduced a mascot called Upy.

This wasn’t just design. I learned how to think in flows, logic, architecture. And I also learned where to go lean, where to build, and where to ignore the noise. Many “AI-driven risk management” platforms were charging high fees, but they really just wanted access to your data so they could learn on your dime. I passed. We built what mattered, ourselves.

Results That Beat the Industry

After one year of operations, our non-performing loan rate was under 20%, in a sector where the average was over 30%. We served people that the traditional system wouldn’t even look at. And we did it with clarity, ethics, and efficiency. It wasn’t perfect. But it worked.

When the Platform Ended and What Came Next

Then the pandemic hit. Capital dried up. High-risk lending became even harder to fund. And eventually, I had to shut it down. It was a tough ending, not just because we had built a solid fintech platform, but because we were seeing a path to profitability. And we were just beginning to unlock the value of rich, real-world data collected from across Mexico, drawn from a segment that’s chronically underbanked and largely overlooked.

At one point, Santander reached out, first to explore investing in or acquiring the business. We negotiated for about eight months. What became clear on both sides was that a bank of that size buys a company on a two-year clock, and the BNPL market would not wait that long. So we changed the structure rather than the outcome: Santander paid to bring me and the model inside immediately, an acqui-hire, and I went on to lead their fintech strategy and rebuild the platform from within the bank. It wasn’t the exit I had imagined. But it was the fastest route to building at scale, and by then I had built enough to earn their trust, so I said yes.

What I Learned

In the end, I learned to build a digital platform from the ground up, with zero previous experience, in my late thirties. No tech background, no cofounder, no roadmap, just the commitment to figure it out, one layer at a time.

I had to learn how to speak to developers, how to think in flows and architecture, how to distinguish between shiny tools and real solutions, how to design around the customer and not the pitch deck. And how to do it lean, because every dollar mattered. It wasn’t easy, it took longer than I expected, I made mistakes, and I burned money. But eventually, it got built and it worked.

That’s the part that stays with me. Not just that I built something, but that I proved to myself, and maybe to others, that it’s still possible to start from scratch, even when it’s late, messy, or expensive. You can teach yourself, adapt, and lead, even in industries that feel closed off to outsiders. You don’t need to be young, technical, or backed by venture capital. You just need to be in it for the right reasons. And willing to keep going when most would stop.